libgo/go/net/cgo_unix.go

   1 // Copyright 2011 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 //go:build cgo && !netgo && (aix || darwin || dragonfly || freebsd || hurd || linux || netbsd || openbsd || solaris)
   6
   7 package net
   8
   9 /*
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <netinet/in.h>
  13 #include <netdb.h>
  14 #include <unistd.h>
  15 #include <string.h>
  16
  17 // If nothing else defined EAI_OVERFLOW, make sure it has a value.
  18 #ifndef EAI_OVERFLOW
  19 #define EAI_OVERFLOW -12
  20 #endif
  21 */
  22
  23 import (
  24         "context"
  25         "syscall"
  26         "unsafe"
  27 )
  28
  29 //extern getaddrinfo
  30 func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int32
  31
  32 //extern freeaddrinfo
  33 func libc_freeaddrinfo(res *syscall.Addrinfo)
  34
  35 //extern gai_strerror
  36 func libc_gai_strerror(errcode int) *byte
  37
  38 // bytePtrToString takes a NUL-terminated array of bytes and convert
  39 // it to a Go string.
  40 func bytePtrToString(p *byte) string {
  41         a := (*[10000]byte)(unsafe.Pointer(p))
  42         i := 0
  43         for a[i] != 0 {
  44                 i++
  45         }
  46         return string(a[:i])
  47 }
  48
  49 // An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
  50 // error number. It's a signed number and a zero value is a non-error
  51 // by convention.
  52 type addrinfoErrno int
  53
  54 func (eai addrinfoErrno) Error() string   { return bytePtrToString(libc_gai_strerror(int(eai))) }
  55 func (eai addrinfoErrno) Temporary() bool { return eai == syscall.EAI_AGAIN }
  56 func (eai addrinfoErrno) Timeout() bool   { return false }
  57
  58 type portLookupResult struct {
  59         port int
  60         err  error
  61 }
  62
  63 type ipLookupResult struct {
  64         addrs []IPAddr
  65         cname string
  66         err   error
  67 }
  68
  69 type reverseLookupResult struct {
  70         names []string
  71         err   error
  72 }
  73
  74 func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
  75         addrs, err, completed := cgoLookupIP(ctx, "ip", name)
  76         for _, addr := range addrs {
  77                 hosts = append(hosts, addr.String())
  78         }
  79         return
  80 }
  81
  82 func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
  83         var hints syscall.Addrinfo
  84         switch network {
  85         case "": // no hints
  86         case "tcp", "tcp4", "tcp6":
  87                 hints.Ai_socktype = syscall.SOCK_STREAM
  88                 hints.Ai_protocol = syscall.IPPROTO_TCP
  89         case "udp", "udp4", "udp6":
  90                 hints.Ai_socktype = syscall.SOCK_DGRAM
  91                 hints.Ai_protocol = syscall.IPPROTO_UDP
  92         default:
  93                 return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
  94         }
  95         switch ipVersion(network) {
  96         case '4':
  97                 hints.Ai_family = syscall.AF_INET
  98         case '6':
  99                 hints.Ai_family = syscall.AF_INET6
 100         }
 101         if ctx.Done() == nil {
 102                 port, err := cgoLookupServicePort(&hints, network, service)
 103                 return port, err, true
 104         }
 105         result := make(chan portLookupResult, 1)
 106         go cgoPortLookup(result, &hints, network, service)
 107         select {
 108         case r := <-result:
 109                 return r.port, r.err, true
 110         case <-ctx.Done():
 111                 // Since there isn't a portable way to cancel the lookup,
 112                 // we just let it finish and write to the buffered channel.
 113                 return 0, mapErr(ctx.Err()), false
 114         }
 115 }
 116
 117 func cgoLookupServicePort(hints *syscall.Addrinfo, network, service string) (port int, err error) {
 118         s, err := syscall.BytePtrFromString(service)
 119         if err != nil {
 120                 return 0, err
 121         }
 122         // Lowercase the service name in the memory passed to C.
 123         for i := 0; i < len(service); i++ {
 124                 bp := (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(s)) + uintptr(i)))
 125                 *bp = lowerASCII(*bp)
 126         }
 127         var res *syscall.Addrinfo
 128         syscall.Entersyscall()
 129         gerrno := libc_getaddrinfo(nil, s, hints, &res)
 130         syscall.Exitsyscall()
 131         if gerrno != 0 {
 132                 isTemporary := false
 133                 switch gerrno {
 134                 case syscall.EAI_SYSTEM:
 135                         errno := syscall.GetErrno()
 136                         if errno == 0 { // see golang.org/issue/6232
 137                                 errno = syscall.EMFILE
 138                         }
 139                         err = errno
 140                 default:
 141                         err = addrinfoErrno(gerrno)
 142                         isTemporary = addrinfoErrno(gerrno).Temporary()
 143                 }
 144                 return 0, &DNSError{Err: err.Error(), Name: network + "/" + service, IsTemporary: isTemporary}
 145         }
 146         defer libc_freeaddrinfo(res)
 147
 148         for r := res; r != nil; r = r.Ai_next {
 149                 switch r.Ai_family {
 150                 case syscall.AF_INET:
 151                         sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
 152                         p := (*[2]byte)(unsafe.Pointer(&sa.Port))
 153                         return int(p[0])<<8 | int(p[1]), nil
 154                 case syscall.AF_INET6:
 155                         sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
 156                         p := (*[2]byte)(unsafe.Pointer(&sa.Port))
 157                         return int(p[0])<<8 | int(p[1]), nil
 158                 }
 159         }
 160         return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
 161 }
 162
 163 func cgoPortLookup(result chan<- portLookupResult, hints *syscall.Addrinfo, network, service string) {
 164         port, err := cgoLookupServicePort(hints, network, service)
 165         result <- portLookupResult{port, err}
 166 }
 167
 168 func cgoLookupIPCNAME(network, name string) (addrs []IPAddr, cname string, err error) {
 169         acquireThread()
 170         defer releaseThread()
 171
 172         var hints syscall.Addrinfo
 173         hints.Ai_flags = int32(cgoAddrInfoFlags)
 174         hints.Ai_socktype = syscall.SOCK_STREAM
 175         hints.Ai_family = syscall.AF_UNSPEC
 176         switch ipVersion(network) {
 177         case '4':
 178                 hints.Ai_family = syscall.AF_INET
 179         case '6':
 180                 hints.Ai_family = syscall.AF_INET6
 181         }
 182
 183         h := syscall.StringBytePtr(name)
 184         var res *syscall.Addrinfo
 185         syscall.Entersyscall()
 186         gerrno := libc_getaddrinfo(h, nil, &hints, &res)
 187         syscall.Exitsyscall()
 188         if gerrno != 0 {
 189                 isErrorNoSuchHost := false
 190                 isTemporary := false
 191                 switch gerrno {
 192                 case syscall.EAI_SYSTEM:
 193                         errno := syscall.GetErrno()
 194                         if errno == 0 {
 195                                 // err should not be nil, but sometimes getaddrinfo returns
 196                                 // gerrno == C.EAI_SYSTEM with err == nil on Linux.
 197                                 // The report claims that it happens when we have too many
 198                                 // open files, so use syscall.EMFILE (too many open files in system).
 199                                 // Most system calls would return ENFILE (too many open files),
 200                                 // so at the least EMFILE should be easy to recognize if this
 201                                 // comes up again. golang.org/issue/6232.
 202                                 errno = syscall.EMFILE
 203                         }
 204                         err = errno
 205                 case syscall.EAI_NONAME:
 206                         err = errNoSuchHost
 207                         isErrorNoSuchHost = true
 208                 default:
 209                         err = addrinfoErrno(gerrno)
 210                         isTemporary = addrinfoErrno(gerrno).Temporary()
 211                 }
 212
 213                 return nil, "", &DNSError{Err: err.Error(), Name: name, IsNotFound: isErrorNoSuchHost, IsTemporary: isTemporary}
 214         }
 215         defer libc_freeaddrinfo(res)
 216
 217         if res != nil {
 218                 cname = bytePtrToString((*byte)(unsafe.Pointer(res.Ai_canonname)))
 219                 if cname == "" {
 220                         cname = name
 221                 }
 222                 if len(cname) > 0 && cname[len(cname)-1] != '.' {
 223                         cname += "."
 224                 }
 225         }
 226         for r := res; r != nil; r = r.Ai_next {
 227                 // We only asked for SOCK_STREAM, but check anyhow.
 228                 if r.Ai_socktype != syscall.SOCK_STREAM {
 229                         continue
 230                 }
 231                 switch r.Ai_family {
 232                 case syscall.AF_INET:
 233                         sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
 234                         addr := IPAddr{IP: copyIP(sa.Addr[:])}
 235                         addrs = append(addrs, addr)
 236                 case syscall.AF_INET6:
 237                         sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
 238                         addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
 239                         addrs = append(addrs, addr)
 240                 }
 241         }
 242         return addrs, cname, nil
 243 }
 244
 245 func cgoIPLookup(result chan<- ipLookupResult, network, name string) {
 246         addrs, cname, err := cgoLookupIPCNAME(network, name)
 247         result <- ipLookupResult{addrs, cname, err}
 248 }
 249
 250 func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
 251         if ctx.Done() == nil {
 252                 addrs, _, err = cgoLookupIPCNAME(network, name)
 253                 return addrs, err, true
 254         }
 255         result := make(chan ipLookupResult, 1)
 256         go cgoIPLookup(result, network, name)
 257         select {
 258         case r := <-result:
 259                 return r.addrs, r.err, true
 260         case <-ctx.Done():
 261                 return nil, mapErr(ctx.Err()), false
 262         }
 263 }
 264
 265 func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
 266         if ctx.Done() == nil {
 267                 _, cname, err = cgoLookupIPCNAME("ip", name)
 268                 return cname, err, true
 269         }
 270         result := make(chan ipLookupResult, 1)
 271         go cgoIPLookup(result, "ip", name)
 272         select {
 273         case r := <-result:
 274                 return r.cname, r.err, true
 275         case <-ctx.Done():
 276                 return "", mapErr(ctx.Err()), false
 277         }
 278 }
 279
 280 // These are roughly enough for the following:
 281 //
 282 // Source               Encoding                        Maximum length of single name entry
 283 // Unicast DNS          ASCII or                        <=253 + a NUL terminator
 284 //                      Unicode in RFC 5892             252 * total number of labels + delimiters + a NUL terminator
 285 // Multicast DNS        UTF-8 in RFC 5198 or            <=253 + a NUL terminator
 286 //                      the same as unicast DNS ASCII   <=253 + a NUL terminator
 287 // Local database       various                         depends on implementation
 288 const (
 289         nameinfoLen    = 64
 290         maxNameinfoLen = 4096
 291 )
 292
 293 func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
 294         var zone string
 295         ip := parseIPv4(addr)
 296         if ip == nil {
 297                 ip, zone = parseIPv6Zone(addr)
 298         }
 299         if ip == nil {
 300                 return nil, &DNSError{Err: "invalid address", Name: addr}, true
 301         }
 302         sa, salen := cgoSockaddr(ip, zone)
 303         if sa == nil {
 304                 return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
 305         }
 306         if ctx.Done() == nil {
 307                 names, err := cgoLookupAddrPTR(addr, sa, salen)
 308                 return names, err, true
 309         }
 310         result := make(chan reverseLookupResult, 1)
 311         go cgoReverseLookup(result, addr, sa, salen)
 312         select {
 313         case r := <-result:
 314                 return r.names, r.err, true
 315         case <-ctx.Done():
 316                 return nil, mapErr(ctx.Err()), false
 317         }
 318 }
 319
 320 func cgoLookupAddrPTR(addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) (names []string, err error) {
 321         acquireThread()
 322         defer releaseThread()
 323
 324         var gerrno int
 325         var b []byte
 326         for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
 327                 b = make([]byte, l)
 328                 gerrno, err = cgoNameinfoPTR(b, sa, salen)
 329                 if gerrno == 0 || gerrno != syscall.EAI_OVERFLOW {
 330                         break
 331                 }
 332         }
 333         if gerrno != 0 {
 334                 isTemporary := false
 335                 switch gerrno {
 336                 case syscall.EAI_SYSTEM:
 337                         if err == nil { // see golang.org/issue/6232
 338                                 err = syscall.EMFILE
 339                         }
 340                 default:
 341                         err = addrinfoErrno(gerrno)
 342                         isTemporary = addrinfoErrno(gerrno).Temporary()
 343                 }
 344                 return nil, &DNSError{Err: err.Error(), Name: addr, IsTemporary: isTemporary}
 345         }
 346         for i := 0; i < len(b); i++ {
 347                 if b[i] == 0 {
 348                         b = b[:i]
 349                         break
 350                 }
 351         }
 352         return []string{absDomainName(string(b))}, nil
 353 }
 354
 355 func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) {
 356         names, err := cgoLookupAddrPTR(addr, sa, salen)
 357         result <- reverseLookupResult{names, err}
 358 }
 359
 360 func cgoSockaddr(ip IP, zone string) (*syscall.RawSockaddr, syscall.Socklen_t) {
 361         if ip4 := ip.To4(); ip4 != nil {
 362                 return cgoSockaddrInet4(ip4), syscall.Socklen_t(syscall.SizeofSockaddrInet4)
 363         }
 364         if ip6 := ip.To16(); ip6 != nil {
 365                 return cgoSockaddrInet6(ip6, zoneCache.index(zone)), syscall.Socklen_t(syscall.SizeofSockaddrInet6)
 366         }
 367         return nil, 0
 368 }
 369
 370 func copyIP(x IP) IP {
 371         if len(x) < 16 {
 372                 return x.To16()
 373         }
 374         y := make(IP, len(x))
 375         copy(y, x)
 376         return y
 377 }